Semiconductor nanocrystals whose dimensions are comparable to the bulk exciton diameter show quantum confinement effects. This is seen most clearly in the optical spectra which shift to blue wavelengths as the size of the crystal is reduced.
A compound semiconductor is a semiconductor material composed of elements from two or more groups of the periodic table. These elements can form binary (2 elements), ternary (3 elements), quaternary (4 elements) or penternary (5 elements) compounds. The most common families of compound semiconductors are III-V (e.g. GaAs, AlGaAs, GaN, GaInP) and II-VI (e.g. ZnS, CdTe, ZnO). But, numerous other compound semiconductor families have been studied (e.g. I-VII, IV-VI, V-VI, II-V etc). A comprehensive source of the basic data of known inorganic semiconductors is contained in Semiconductors: Data Handbook by Madelung, Springer-Verlag press; 3rd ed. edition (November 2003).
Semiconductor nanocrystals made from a wide range of materials have been studied including many II-VI and III-V semiconductors. II-V semiconductor compounds such as ZnN and ZnAs are known [Paniconi et al. J. Solid State Chem 181 (2008) 158-165] and [Chelluri et al. APL 49 24 (1986) 1665-1667] in the form of thin films or powders. For nanocrystals, [Buhro et al. Polyhedron Vol 13. (1994) p 1131] report on the synthesis of ZnP nanoparticles.
III-V semiconductors are numerous and one of the most interesting classes of III-V semiconductors is the III-nitrides, such as AlN, GaN, InN and their respective alloys. These are used for the manufacture of blue light-emitting diodes, laser diodes and power electronic devices. Nitrides are also chemically inert, are resistant to radiation, and have large breakdown fields, high thermal conductivities and large high-field electron drift mobilities, making them ideal for high-power applications in caustic environments [Neumayer at. al., Chem., Mater., 1996, 8, 25]. The band gaps of aluminium nitride (6.2 eV), gallium nitride (3.5 eV) and Indium nitride (0.7 eV) [Gillan et. al., J. Mater. Chem., 2006, 38, 3774] mean that nitrides span much of the ultraviolet, visible and infrared regions of the electromagnetic spectrum. The fact that alloys of these materials have direct optical band gaps over this range makes these very significant for optical devices.
Solid-solution GaN/ZnO nanocrystals have been reported [Han et al. APL. 96, (2010) 183112] and were formed by combining GaN and ZnO nanocrystals as a crystal solid. The ratio of ZnO to GaN was controlled by varying the nitridation time of a GaZnO precursor.
III-IV-V semiconductors, for example SiGaAs, have been reported in thin film form (for example in U.S. Pat. No. 4,213,781), but have not been reported not in nanoparticle form.
F. Zong et al. propose, in “Structural properties and photoluminescence of zinc nitride nanowires”, Applied Physics Letters (8691034 IEE INSPEC, 2005) and in “Nano-structures and properties of zinc nitride prepared by nitridation technique”, Proceedings of Fifth Pacific Rim International Conference on Advanced Materials and Processing”, Beijing, 2004 (8418308 IEE INSPEC), the synthesis of zinc nitride nanowires by reacting zinc powder with ammonia gas. By a “nanowire” is meant a structure in which two dimensions are of the order of nanometers and the third dimension is much larger, typically of the order of micrometers.
US 2009/0121184 proposes a “hydrogen storage material”, which can store hydrogen and release it when the material is heated. The material contains a mixture and a reaction product of a metal hydride and a metal amide.
US 2003/167778 proposes a nanostructure that contains hydrogen, for example for use in a hydrogen storage system. It lists magnesium nitride as a possible material, and suggests milling the material such that the resulting material “will contain some nanostructured storage material”.
Y Ye et al. propose an amorphous zinc oxynitride semiconductor material, in “High mobility amorphous zinc oxynitride semiconductor material for thin film transistors”, Applied Physics Letters (10930195 IET INSPEC, 2009).
U.S. Pat. No. 6,527,858 proposes the fabrication of a ZnO single crystal, by a process in which atomic zinc and oxygen are supplied to a growth chamber, together with atomic nitrogen (as a p-type dopant) and atomic gallium (as an n-type dopant).